Update: For information on the current year tax filing delay, see tax refund delay .
Tax Delay 2010
Do you itemize deductions ? If so, you might be subject to the IRS tax filing delay this year.
With the passing of the Social Security tax break , deductions for state and local sales taxes, an AMT patch , tuition and fees deductions  and teacher expenses so late in the year (December 17th, 2010), the IRS has been quite busy.
The IRS is so busy in fact, that they are expecting delays in processing filed 2010 tax returns as well as a refund delay  for those who are eligible in 2011.
You can use the Where’s My Refund?  tracker to check the status of your tax refund.
Who the IRS Tax Delay Applies To
When Can You File Your Tax Return?
The IRS cannot begin to process tax forms until mid-February, and suggest that you do not send your forms in until they are ready to receive them (they have not given out a date yet). We’ll let you know when the delay tax filing date is published.
Update: The IRS announced that they will begin to process paper and efiled returns subject to the delay on Feb. 14. Another delay is possible: Will a Government Shutdown Delay Your Tax Refund? 
Companies like TurboTax  will allow you to file your form as usual (which began last week), but will not file the form with the IRS until given the go ahead.
So if you itemize your taxes, this year it is best to be later rather than to file early on in the tax season, with the tax refund delay.